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Chain Reactions Reignited At Fukushima
mdsolar writes "Radioactive byproducts indicate that nuclear chain reactions must have been burning at the damaged nuclear reactors long after the disaster unfolded. Tetsuo Matsui at the University of Tokyo, says the limited data from Fukushima indicates that nuclear chain reactions must have reignited at Fuksuhima up to 12 days after the accident. Matsui says the evidence comes from measurements of the ratio of cesium-137 and iodine-131 at several points around the facility and in the seawater nearby."
If you melt the fuel, you can get localized criticalities.
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How, without a moderator?
My understanding is that LEU (low-enriched uranium) cannot achieve criticality without a moderator to slow down the neutrons?
Can anyone with a nuclear physics/engineering background give any explanation of how you can get a chain reaction without moderator?
Ok, they were cooling the reactor with water, and water is a moderator, but the water was also boronated, which should cancel the moderation property of water, shouldn't it?
More and more I see the attempt to design and operate Nuke plant as a very dangerous game of Whack-a-mole. Operator error, Wham, Design error, Wham, Maintenance failure, Wham. Earthquakes. Wham. Tsunamis, Wham. Terrorism, Wham,
and, what do we do with the waste for the next 20,000 years? Wham, Wham, Wham, Wham........
Miss one time, game over.
Kurt
And operating a coal plant is akin to all the moles poked out of their holes and looking at you while you shrug and say "working as intended."
"I zero-index my hamsters" - Willtor (147206)
It did scram completely. The decay heat, which is 7% of 1000 MW boiled away all the water they lost the ability to pump, and then melted the zircalloy fuel rods into a pile of molten slag in places. That slag then has the geometrical configuration to do some more fission. Ironically, they may have had no problems if they didn't scram, as the reactor could then drive power to the cooling pumps, as opposed to relying on diesel generators.
There are reactor designs that currently exist that are more resilient to meltdowns. Most notably, thorium molten salt reactors, but there are only a handful of experimental reactors in existence. There is also the CANDU reactor primarily used and designed in Canada which is a uranium heavy water reactor.
I will agree with you that the ancient nuclear technology most reactors use today is not that safe, but more modern reactors have solved that issue. The only problem has been rolling out thorium and CANDU reactors.
And WRT your comment on terrorism, there's a video on Youtube I've seen that debunks the whole "flying a plane into a reactor" myth. Nuclear plants have concrete walls that are like 10 feet thick and the plane collapses on it self and does nothing to the wall.
You can get rid of the waste whenever we are smart enough to switch to thorium fueled fluoride salt reactors which are inherently safer, much more efficient using only a fraction of a much more plentiful fuel to produce the same energy. The small amount of unusuable nuclear byproducts of a thorium reactor have much more manageable half-life of around 330 years. The useful byproducts include many things that are otherwise difficult to produce like the isotope of plutonium used to power deep space probes, bismuth-213 which is used in cancer treatments and has a 45-minute half life.
But to your point the best thing is the inherent safety, LFTRs (liquid fluoride thorium reactors) can be easily designed to passively shutdown rather than requiring active cooling inside the operating core which is the problem with all water cooled reactors which is all we have today. The funny thing is we have tested and proven this technology, we know it works, but the unsafe technology that produces weaponizable nuclear components and huge amounts of dangerous waste is so lucrative and entrenched that current nuclear players have no financial incentives to make the shift.
And the fact that a LFTR can reduce the waste we have produced from current nuclear technologies and turn it into more energy and more manageable waste.
Sensationalistic, atleast.
Did they restart? Techreview says "yes", Nature says "No":
http://blogs.nature.com/news/2011/05/analysis_suggests_fukushima_re_1.html
"The decay heat, which is 7% of 1000 MW"
IIRC, the reactors were 1000MW *electrical* output. Because of thermal efficiencies of steam generators of around 35%, I believe that means the thermal output of each reactor would have been about 1000/.35 ~= 2800 MW thermal energy.
So, instead of 7% of 1000MW = 70MW, I think you're looking at 7% of 2800 = 196MW.
That's a LOT of heat to get rid of, even if it is a small percentage of the 2800MW full output.
With difficulty, but it's possible.
As for any claim that Thorium is some magic pixy dust that prevents all forms of nuclear accident.... pah.
Watch this Heartland Institute video
Sorry, You did not address waste issue. Wham. Wham
What waste issue, you do realize you're surrounded by radiation now right? Granite counter tops, bananas, air line travel [boom headshot]. Btw some thing will kill you, be it cold, or starvation b/c you don't live next to the food you eat, or perhaps bacteria growing in the natural environment that decided you were a good place to set up shop. But hey, you keep trying to make everybody confirm to your nanny-state, gaia fueled fantasy and let me know how that works out.
I laughed at the weak who considered themselves good because they lacked claws.
So what you're saying is:
It was the worst natural disaster in Japan's history, one that was the perfect storm of conditions, all affecting an ancient design of plant which was NOT designed to handle such disasters, and yet despite this- still to this very day- has not had a substantial meltdown (some radiation leakage is not crowd on the beach in Melbourne)... and you're *complaining*?
Inevitable car analogy is as follows. If I own a regular Toyota Prius, there's a reasonable expectation that if I get into a fender bender I won't die. It's engineered to tolerate that. The car may be a write off, but I'm fairly safe.
But if a TANK shoots my Prius? Well, then I'm fucked. I'll die and it's *not Toyota's fault*, much less the fault of the automotive industry at a whole. You accept that, right? You accept that anything built by anyone, ever, is built to a limited amount of tolerance, and beyond that failure is not the fault of the manufacturer, let alone the whole industry?
In this metaphore, a tank shot my Prius in the engine block... and to the astonishment of most the Prius fucking TOOK IT. That armour-piercing tank shell bounced off like a motherfucker, leaving a huge dent, and shaking the car so I wacked my head, but hey. I'm alive and whole. I walked away after the worst imaginable thing happened, far beyond the design specifications of the vehicle. Yeah, there was a little blood-slash-radiation leakage from my head, but it's not that bad. I could have a concussion. I should probably get checked out, but it could have been MUCH worse. Furthermore, I am astounded on how this Prius is eating tank shells. That's some serious engineering work right there. Damn, dog... ... and yet, people are still like, "Oh, but I'm bruised a little bit, it didn't protect me completely. Priuses are so unreliable!"
Seriously.
Tank.
Prius.
Tepco might be incompetent lying morons, but the reason why the old plant was still around was in no small part because of anti-nuclear fear-mongering ("Not in MY backyard!"). That's the reason that newer, far more safter, reactors are not everywhere. Because constructing new nuke reactors is verboten, like we're still in the 70's or some shit.
If we treated nuclear power with the respect it deserves, keeping the technology up to date and learning from our mistakes... then we can progress.
Check out my sci-fi book "Lacuna" at http://goo.gl/MVxX8
Horse shit. Pure horse shit. Radiation levels at the moment are still extremely minor. Plant workers are still not exceeding their yearly allotment, they're being pulled out before hand. The yearly allotment is below the level that shows even a minor increase in cancer rates. The government has stopped fishing mostly for trust reasons - it's unlikely that anyone would've been made sick, but they want people to feel safe buying the fish when they do open it up.
This is a big problem, and it shouldn't have happened. But this event has made a few people sick (like a sunburn) for a few days because they didn't follow proper protocol. Meanwhile, the triggering event has killed, what, 20,000? Versus a couple people with minor injuries.
If you have evidence to refute the above points, I'd love to see your citations. I've been following this pretty closely, so I'd be very interested to see if I've been wrong.
But it seems like you're just making stuff up. There are plenty of facts in this debate. Don't go inventing nonsense just because the facts don't fit your opinion.
I'm not a nuclear fanboy, by any means. As an engineer, current plants make me nervous because they rely on active safety. But I'm more annoyed that NIMBYs aren't allowing research and production of the intrinsically-safe plants, than I am about the operators of the plant. Nuclear plants "feel" unsafe? Well they have just about the best safety record of all industrial facilities. This particular plant had multiple failures after design specifications were well exceeded, and even then the problems they've had have been extremely minor in relative and absolute terms.
In short, you're being irrational.
I have developed a truly marvelous proof of this comment, which this signature is too narrow to contain.
It started to carry a negative connotation when some people started using junk science to raise false alarms. Look at Helen Caldicott telling everyone that Chernobyl resulted in millions of deaths, and that Fukushima will result in millions of cancers.
She repeatedly appeals to a single source - a Greenpeace "Report" which they somehow managed to get the NYAS to publish without any peer review, which specifically states that it does not use standard scientific analysis methods because those methods don't give the results the report author wants to find.
She ignores all the other science which has been done to determine the results of Chernobyl, decrying it all as a massive "cover up" and "fraud". There's only one report in the world, apparently, which tells "the truth". These people cherry pick their sources to get the alarming results they want to find.
See: Confirmation Bias
That is the sense that most people use when they pejoratively use the term 'alarmist' - someone who spreads FUD which is not based on sound science.